Tritium, which is a radioactive isotope of the element hydrogen, would a powerful source in fuel future nuclear fusion reactors. Tritium acts much like hydrogen and is easily disbursed in environmental and biological systems. The risk assessment of tritium is one of the major issues arising in the development of the fusion reactors.

Exposure to tritium increases the risk of developing cancer as with all ionizing radiation. Cancer risk of tritium in man must be estimated based on experimental studies alone due to lack of human epidemiological data. Although the effects of tritium in mice have been described in many reports, the available information is not sufficient to accurately estimate risk from tritium exposure.

To evaluate cancer risk from tritium exposure, we developed Rev1 transgenic mice as a high radiation sensitive assay system. Rev1 has a central role in translesion DNA synthesis (TLS), which is known as error-prone DNA repair. It has been reported that absence of Rev1 sensitizes to a variety of DNA damaging agents including ionizing radiation. Overexpression of Rev1 enhanced chemical-induced tumor development in mice. From these studies, we suggest that Rev1 transgenic mouse may be a useful model system for the study of risk estimation of tritium induced cancers.